1. Field of the Invention
The present invention relates to an optical disk, an optical disk recording apparatus, an optical disk recording method, an optical disk playback apparatus, and an optical disk playback method and, for example, can be applied to a high-sound-quality optical disk which can be played back by a conventional compact disk player and to an apparatus associated with this optical disk. The present invention aims at supplying contents which can be played back by a conventional optical disk apparatus and which plays back at still higher quality by recording second information by partial changes of the optical characteristics of such a degree which does not affect the detection result of first and second areas detected by the irradiation of a laser beam.
2. Description of the Related Art
Conventionally, in compact disks, an audio data stream is EFM-modulated (Eight-to-Fourteen Modulated), forming pits and space in sequence according to a length corresponding to a period 3T to 11T with respect to a predetermined reference period T, thereby allowing audio data, etc., to be recorded.
More specifically, in a compact disk, by subjecting an audio signal to an analog-to-digital conversion process, audio data is created, and an error correcting code (ECC), etc., is added to this audio data. In the compact disk, an 8-bit data stream created in this manner is interleaved and is further EFM-modulated. In the compact disk, each data of 8 bits is converted into data of 14 bits by this EFM-modulation, and further, each data of 14 bits is connected by 3 bits of coupling data in order to be converted into serial data.
In the compact disk, by performing on-off control of a laser beam in accordance with this serial data, pits and lands are formed in sequence, so that, by using the period T of a channel clock of this serial data as a reference period, pits and space are repeated according to the length corresponding to a period which is an integral multiple of this reference period T, thereby allowing audio data to be recorded.
With respect to this, in the compact disk player, returning light obtained by irradiating a laser beam onto a compact disk is received and the light-received result is processed, thereby generating a playback signal whose signal level varies according to the pit and spaces. Furthermore, this playback signal is identified by binary values in order to demodulate the serial data created during recording, and this serial data is processed in accordance with the process during recording, thereby playing back the audio data.
As an optical disk on which both video data and audio data are recorded instead of audio data, there is a DVD (Digital Video Disk). Also in a DVD, similarly to the compact disk, pits and spaces are repeated according to a length of an integral multiple of a length corresponding to a reference period T, thereby allowing video data and audio data to be recorded.
For optical disks for compact disk players, etc., which have already been distributed on the market, if various content can be provided at even higher quality, advantages can be expected, such as the application range of this type of optical disk being expanded.
In this case, it is desired that this type of content can also be played back by a conventional compact disk player.
The present invention has been achieved by considering the above points. An object of the present invention is to provide an optical disk which can supply contents of higher quality while being able to be played back even by a conventional optical disk apparatus, and an optical disk recording apparatus, an optical disk recording method, an optical disk playback apparatus, and an optical disk playback method which are applied to this optical disk.
To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided an optical disk, wherein second information is recorded by partial changes of the optical characteristics of first and second areas, such changes being of such a degree which does not affect detection results of the first and second areas detected by the irradiation of a laser beam, and the second information is information capable of improving the quality of contents represented by first information.
According to a second aspect of the present invention, there is provided an optical disk recording apparatus, wherein the signal superimposition means superimposes second information onto a modulation signal in such a manner as to provide partial changes of the optical characteristics to first and second areas to such a degree as not to affect detection results of the first and second areas which are detected by the irradiation of a playback laser beam.
According to a third aspect of the present invention, there is provided an optical disk recording method comprising a step of: superimposing second information onto a modulation signal so that partial changes of the optical characteristics to first and second areas are provided to the first and second areas to such a degree as not to affect detection results of the first and second areas which are detected by the irradiation of a playback laser beam.
According to a fourth aspect of the present invention, there is provided an optical disk playback apparatus comprising: first information playback means for playing back first information recorded by a repetition of a first area and a second area exhibiting the different optical characteristics by identifying by binary values the playback signal by using a clock as a reference; binarization means for binarizing the playback signal in order to generate a binary signal; second information playback means for detecting second information recorded by partial changes of the optical characteristics of at least one of the first and second areas by determining the signal level of the playback signal at a predetermined timing on the basis of the binary signal; and combining means for combining the first and second information.
According to a fifth aspect of the present invention, there is provided an optical disk playback method comprising the steps of: playing back first information recorded by a repetition of a first area and a second area exhibiting different optical characteristics with respect to the irradiation of a laser beam according to a length of substantially an integral multiple of a predetermined reference length; playing back second information recorded by partial changes of the optical characteristics of one of the first and second areas, such changes being of such a degree which does not affect detection results of the first and second areas detected by the irradiation of the laser beam; and combining the first and second information and outputting it.
According to the optical disk in accordance with the first aspect of the present invention, second information is recorded by partial changes of the optical characteristics of at least one of a first area and a second areas, such changes being of such a degree which does not affect detection results of the first and second areas detected by the irradiation of a laser beam, thereby allowing the second information to be recorded without obstructing the playback of first information. As a result, by making this second information to represent information capable of improving the quality of contents represented by the first information, it is possible to supply still higher quality contents which can be played back even by a conventional optical disk apparatus.
Also, according to the optical disk recording apparatus in accordance with the second aspect of the present invention, the signal superimposition means superimposes second information onto a modulation signal so that partial changes of optical characteristics are provided to at least one of the first and second areas to such a degree which does not affect detection results of the first and second areas which are detected by the irradiation of a playback laser beam. Thus, it is possible to record the second information without obstructing the playback of first information and possible to supply still higher quality contents which can be played back even by a conventional optical disk apparatus.
Also, according to the optical disk recording method in accordance with the third aspect of the present invention, second information is superimposed onto a modulation signal so that partial changes of optical characteristics are provided to at least one of the first and second areas to such a degree which does not affect detection results of the first and second areas which are detected by the irradiation of a playback laser beam. Thus, it is possible to record the second information without obstructing the playback of first information and possible to supply still higher quality contents which can be played back even by a conventional optical disk apparatus.
Also, according to the optical disk playback apparatus in accordance with the fourth aspect of the present invention, the first information playback means plays back first information recorded by a repetition of a first area and a second area exhibiting different optical characteristics by identifying by binary values a playback signal by using a clock as a reference. The binarization means binarizes the playback signal in order to generate a binary signal. The second information playback means detects second information recorded by partial changes of the optical characteristics of at least one of the first and second areas by determining the signal level of the playback signal at a predetermined timing on the basis of the binary signal. The combining means combines the first and second information. Thus, for example, it is possible to play back high-quality contents by playing back first information recorded by pits and spaces and second information recorded by partial changes, etc., of the width of the pit.
According to the optical disk playback method in accordance with the fifth aspect of the present invention, first information recorded by a repetition of a first area and a second area exhibiting different optical characteristics with respect to the irradiation of a laser beam is played back according to a length of substantially an integral multiple of a predetermined reference length. Second information recorded by partial changes of the optical characteristics of at least one of the first and second areas, such changes being of such a degree which does not affect detection results of the first and second areas detected by the irradiation of the laser beam is played back, and the first and second information are combined. Thus, it is possible to supply high-quality contents by playing back first information recorded by, for example, pits and spaces and second information recorded by partial changes, etc., of the width of the pit.
The above and further objects, aspects and novel features of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.